The present invention relates to a tandem brake booster adapted for use in automotive vehicles, and more particularly to an improvement of a housing assembly for the tandem brake booster which includes a front shell having an annular opening end portion in the form of an annular stepped flange, a rear shell having an outer peripheral portion coupled within the annular stepped flange of the front shell and opposed to an annular shoulder of the stepped flange, and a partition wall member assembled within the front shell to subdivide the interior of the coupled shells into front and rear chambers, the partition wall member having an annular opening end portion in the form of an annular radial flange interposed between the annular shoulder of the front shell and the outer peripheral portion of the rear shell.
In such a conventional housing assembly for tandem brake boosters as described above, the annular stepped flange of the front shell is formed with a plurality of circumferentially spaced radial projections which are engaged with the outer peripheral portion of the rear shell to fasten the partition wall member and the rear shell to the front shell, and the outer peripheral portion of the rear shell and the annular radial flange of the partition wall member each are formed with a plurality of circumferentially spaced radial recesses which are arranged to permit removal of the partition wall member and the rear shell from the front shell when opposed to the corresponding radial projections of the front shell.
In the above-described attachment of the rear shell, both the radial recesses of the rear shell and the partition wall member must be opposed to the corresponding radial projections of the front shell for removal of the rear shell and the partition wall member. For this reason, as is illustrated in FIGS. 5 and 6, the conventional partition wall member (1) is formed at its annular radial flange with an axial projection (1a), and the conventional rear shell (2) is formed at its outer peripheral portion with an axial projection (2a) which is coupled over the axial projection (1a) for rotation therewith. If in detachment the partition wall member (1) and the rear shell (2) are rotated clockwisely in error, the radial projection (3b) of front shell (3) will be raised by abutment against the axial projection (2a) of rear shell (2), resulting in damage or deformation of the radial projection (3b) of front shell (3). Such damage or deformation of the radial projection (3b) will cause loose attachment of the partition wall member (1) and the rear shell (2). Since in attachment of the rear shell (2), the axial projection (1a) of partition wall member (1) is concealed by the outer peripheral portion of rear shell (2), it is difficult to confirm whether or not the axial projection (2a) of rear shell (2) is coupled over the axial projection (1a) of partition wall member (1).